Serious problems are associated with the predominantly prevalent technology of using fossil fuels for power production. Carbon emission on burning of these fuels causes environmental degradation and global warming. Their reservoirs are depleting fast and would not last long. Also, their major supply comes from a limited number of countries, mostly located in a small region of the world. This gives rise to fears about energy security, particularly among the developing countries. It is, therefore, necessary to develop an alternative, which will be free from these drawbacks. Solar Energy is an attractive possibility, because its supply is copious, it causes nil carbon emission, and its potential for producing power is enormous. Various attempts, consequently, have been done, and are being done, to harness solar energy by collecting and concentrating it.
The technologies available for concentrating solar energy are as follows;
a) Parabolic Trough Collectors (PTC), which concentrate solar rays at a focal line.
b) Fresnel Lenses (Reflecting Type), in which strips arranged in a two dimensional array over a large area of land, reflect solar rays incident on them towards the receiver pipe. Each strip is to be solar tracked separately.
c) A dish type parabolic reflector, where solar beam is concentrated at its focal point. It needs two way tracking.
d) Heliostats consist of small rectangular pieces of plane mirror, distributed in a two dimensional array over a large area of land and each such mirror is tracked separately throughout the day, such that all the reflected rays always hit the target, the target being the top chamber of a tower located at the center of the land.
Since the sun has continuous diurnal and seasonal movements in the sky, the angles of the incident solar rays upon the concentrators continuously vary. To accommodate this continuous change, various movable arrangements of reflecting surfaces, or receivers have been coupled with various control means to cause the reflecting surfaces or receivers, or both to automatically track the sun. The solar tracking for trough type collectors is along one axis. The dish needs a ‘two-axes tracking’. This demands an elaborate support structure, and an elaborate mechanism to continuously follow the sun in the sky. Fresnel reflectors need tracking about one axis, but all the reflector strips here have to be held separately and rotated independently; because their orientations at any given time depend, on their positions, vis-a-vis the receiver pipe. This demands, again, an elaborate arrangement to hold and rotate the strips.
The solar collectors are essentially spread over large open grounds. They, therefore, have to negotiate high wind pressure under strong windy conditions. Their support structures in the present art, therefore, are required to be sturdy enough to withstand a heavy wind load. This adds to the cost of support structure.
To overcome these difficulties encountered in the present art, a solar collector with a simpler tracking arrangement and having a very small wind load even under strong windy conditions is required.
Another problem is regarding the requirement of land for a solar collector. The rectangular shaped reflectors in Solar Tower collectors occupy a large area of ground. Further, the said reflectors have to be spaced with sufficient intermediate gaps so as to avoid their shadows on one another. Similarly, in the case of Fresnel type collectors, sufficient gap needs to be provided between any two adjacent strips to avoid mutual blocking of rays by them.
As a result, the area of land required for a solar collector installation is far greater than the area of the solar field; i.e. the actual area, over which solar radiation is being captured by the collector. It is desirable, that the area of land required for a solar collector should not exceed much the area of the solar field.
It is thus, clearly evident from the foregoing description that although solar collector systems are potentially a highly desirable means for providing usable energy, there are many drawbacks associated with such systems. It would be beneficial to provide a solar collector system which is capable of substantially eliminating the problems encountered with past solar collectors.